Vehicle security systems are widely used to deter vehicle theft, prevent theft of valuables from a vehicle, deter vandalism, and to protect vehicle owners and occupants. A typical automobile security system, for example, includes a central processor or controller connected to a plurality of vehicle sensors. The sensors, for example, may detect opening of the trunk, hood, doors, windows, and also movement of the vehicle or within the vehicle. Ultrasonic and microwave motion detectors, vibration sensors, sound discriminators, differential pressure sensors, and switches may be used as sensors. In addition, radar sensors may be used to monitor the area proximate the vehicle.
The controller typically operates to give an alarm indication in the event of triggering of a vehicle sensor. The alarm indication may typically be a flashing of the lights and/or the sounding of the vehicle horn or a siren. In addition, the vehicle fuel supply and/or ignition power may be selectively disabled based upon an alarm condition.
A typical security system also includes a receiver associated with the controller that cooperates with one or more remote transmitters typically carried by the user as disclosed, for example, in U.S. Pat. No. 4,383,242 to Sassover et al. The remote transmitter may be used to arm and disarm the vehicle security system or provide other remote control features from a predetermined range away from the vehicle.
Other vehicle security systems may be associated with the ignition of the vehicle. More particularly, one type of conventional vehicle security system includes a passive transponder either carried by the keychain or embedded in the ignition key. When the transponder is positioned adjacent the ignition switch, the transponder is inductively powered and transmits a uniquely coded signal to a receiver in the vehicle. When a properly coded transponder is detected, the vehicle engine may be allowed to start, for example. In other words, an ignition or fuel cutoff is normally operative to prevent the engine from starting or running, unless the proper transponder is sensed. Accordingly, vehicle security is increased. In addition, the security system may have multiple transponders capable of disabling the ignition or fuel cutoff to thereby permit operation of the vehicle. These uniquely coded transponders may be added or deleted from the vehicle controller. Unfortunately, the owner of the vehicle may not know that a transponder has been added without authorization.
Another variation of vehicle security systems includes a reader or sensor, such as for sensing biometric information from a user. For example, the fingerprint of a user may be sensed and compared against a previously learned reference fingerprint to allow opening of the vehicle door or starting of the engine. As biometric sensors become more rugged, reliable and less expensive, their use in vehicle control systems is expected to increase. Unfortunately, conventional vehicle security systems using remote transmitters, transponders, and even biometric readers are still subject to a security threat based upon unauthorized learning of a uniquely coded transponder, token, or biometric characteristic, for example. Once such a code or identifying characteristic has been learned by a would-be thief without the owner's knowledge, the thief can return to the vehicle and defeat the security system.